Microbalites are associated with late transgressive to highstand systems tract deposits and sediment starvation surfaces and hardgrounds. It is of importance to study microbialites because of three reasons as follows: microbialites can be used as a better indicator matter of palaeoenvironment and palaeoclimate; the pat tern of organic matters can be evaluated by analyzing their biomarkers in formations; the hydrocarbon generating ability of source rock can be assessed by anal yzing organic matters in microbialites. The formation containing microbialites or carbonate microbial crusts which formed on the inner ramp is commonly close to marine source rock or directly overlaid by marine oil shale. Therefore, when argillaceous beds immediately overlying the grainstone and packstone reservoir serve as the seal rocks, this kind of strata will be apt to become better traps if the caprock has a good seal ability. If microbial buildups coexist with reefs especially coral reefs, the coefficient of permeability and the porosity of the microbial reef buildups could be elevated greatly. Research on the microbialites and carbonate microbial crusts in sedimen tary basin provides new ideas for petroleum exploration and trap forecasting.